Spurred by a new "antisnooping" regulation, at least 18 federal agencies have notified the General Services Administration that they don't monitor phone calls from information-seekers without their consent.

The regulation was designed to curb a practice common among federal agencies listening in when citizens called for tax information or help on other matters. Such monitoring was normally done with advance word to government employes answering phones but without notice to outside callers.

According to a survey last year, the Internal Revenue Service routinely assigned supervisors to listen in on 325,000 calls a year from taxpayers seeking information. The IRS monitored the calls to see if its employes were giving accurate and courteous answers. The only notice to a caller that a third party might be listening was given inconspicuously in the federal income-tax form.

A decision by President Carter to ban such snooping in the White House and demands by Sen. Max Baucus (D-Mont.) and Rep. Dale Kildee (D-Mich.) that the government curb it led to promulgation of the GA rule.

The regulation, published last June, proved weaker than some wanted. Paul Goulding, then acting GSA administrator, said all electronic recording and monitoring should be banned except in national security cases or under court order.

However, objections from a number of agencies including IRS and the Justice Department, led to a less stringent rule.

Under the new rule and existing law, if neither the caller nor the employer who answers gives advance consent, then monitoring is allowed only under court order or in special national security situations.

The new rule still allows agencies to monitor calls with only one-party consent (that is the consent of the government employe, but without notice to the caller), if strict records are kept and the head of the agency called authorizes the monitoring. The practical effort is that criminal investigators can monitor calls without court order, if agency employes agree.

But in one instance the new rule does involve an important restriction. Where the monitoring is done purportedly to determine if government employes are giving courteous and accurate anwers to the public, the agency is barred from using in formal proceedings anything it hears against the caller. For example, the Social Security Administration or the IRS can't use information picked up in routine service calls to challenge someone's benefits or look into his or her tax returns.

And the GSA, in a letter to Baucus and Kildee, said a recent survey shows that 18 agencies are going beyond this rule and either declaring they don't monitor, or will only with the consent of both parties, even though the rule requires only one-party consent.

The 18 include Social Security, its parent Health, Education and Welfare Department, the Housing and Urban Development Department, Veteran's Administration, Nuclear Regulatory Commission, Environmental Protection Agency, Civil Rights Commission, U.S. Courts Administrative Office and a number of smaller ones.

A number of other departments or units, such as IRS, Commerce, Interior Department, and Transportation Deapartment, hadn't been heard from at the time of the release of the letter.